Tutorial
The JWT decoder is easy to use. Here is a detailed guide:
Paste Token: Paste your JWT Token string in the input area. JWT Tokens consist of three parts separated by dots (.): Header, Payload, and Signature.
Auto Decode: After input, the tool automatically decodes the token. Header and Payload are Base64Url decoded and displayed as formatted JSON. Signature is shown as a raw Base64Url string.
View Info: Decoded results include: Header with algorithm type (alg) and token type (typ); Payload with all claims such as sub (subject), iat (issued at), exp (expiration time); and the signature.
Expiration Check: If the Payload contains an exp field, the tool automatically compares it with the current time to show whether the token has expired and the remaining valid time.
Use Cases
API Debug: When debugging RESTful APIs, you often need to check JWT Token content to confirm user identity, permissions, and expiration status. This tool lets you quickly decode tokens without adding debug logic to your code.
OAuth2.0 Debugging: In OAuth2.0 flows, Access Tokens and ID Tokens often use JWT format. Decoding these tokens helps understand authorization scope, user info, and token validity.
Security Audit: When auditing web applications, you need to check whether JWT Tokens contain sensitive information, whether expiration policies are properly configured, and whether secure signing algorithms are used.
Knowledge Base
JWT Structure: JWT consists of three parts: Header (token type and algorithm) β Payload (claims/data) β Signature (signature verification). Each part is Base64Url encoded, separated by dots, in the format xxxxx.yyyyy.zzzzz.
Common Claims: iss (issuer), sub (subject), aud (audience), exp (expiration time), nbf (not before), iat (issued at), jti (JWT ID) are RFC 7519 standard registered claims.
Security Notes: JWT can be decoded by anyone, so never store sensitive information like passwords in the Payload. JWT security relies on signature verification. This tool only decodes tokens but does not verify signatures. In production, always verify token signatures and expiration.
FAQ
What is the JWT Decoder tool?
The JWT (JSON Web Token) Decoder is an online tool that can parse JWT Token parts (Header, Payload, Signature), decode Base64Url-encoded content into readable JSON format, for debugging and checking token content.
JWT Token - Is It Safe?
JWT Tokens can be decoded by anyone, so never store sensitive data in the Payload. JWT security relies on signature verification - only parties with the secret key can verify token integrity. This tool decodes but does not verify signatures.
Which JWT algorithms are supported?
Supports identifying all common JWT signing algorithms including HMAC (HS256, HS384, HS512), RSA (RS256, RS384, RS512), and ECDSA (ES256, ES384, ES512). The tool displays the algorithm type declared in the Header.
Is token data uploaded to servers?
No. All decoding runs locally in your browser. JWT Tokens are never uploaded to any server, ensuring your data security.
How to check if a JWT is expired?
The JWT Payload typically contains an exp (expiration time) field as a Unix timestamp. This tool automatically detects the exp field and compares it with the current time, showing whether the token has expired and the remaining valid time.